1C2 ESSENTIALS OF BACTERIOLOGY. 



less deeply than some similar bacilli. Spores have not yet been 

 found ; small oval spaces appear in some of the degenerated 

 bacilli just at one end, but these bacilli are less resistant than 

 those without this so-called spore ; they do not liquefy gelatine. 



FIG. 50. FIG. 51. 



" 



, i/ /' 



, Typhoid fever bacillus in pure cul- Bacillus of typhoid fever. 



ture. 650 diameters. 



Growth. They are facultative anaerobic ; grow best at 37 

 C., but can also develop at ordinary room temperature. All 

 nutrient media can be used as culture ground. They develop 

 chiefly on the surface, and very slowly. 



Colonies on Gelatine Plates. Two forms ; the ones near the 

 surface spread out like a leaf, transparent with bluish fluor- 

 escence. The deeper ones appear as whetstone crystals of 

 uric acid, the same yellowish tinge. 



In five days they attain to 3 millimetres in diameter. 



On Potato Gelatine. The colonies do not have the yellow 

 color, they are transparent, later on they become dark brown 

 with green iridescence. 



Stab Cultures. Mainly on the surface a pearly layer. 



Stroke Cultures. A transparent thick layer. 



Potato. The growth here is quite characteristic. At 37 C. 

 in 48 hours a moist transparent film is formed over the whole 

 surface, but so transparent that it can hardly be seen without 

 close observation. If a small portion of this is placed under a 

 microscope, it will be seen swarming with bacilli. 



The growth never becomes more prominent ; the potato must 

 have a neutral or acid reaction. 



